1. Relevant Prior Art
Such lasers are for example described in the Applicant's DE-OS [German Laid-Open Patents] 3,734,570 and 4,029,187. These lasers have a square shape. However, they can have a rectangular shape or, in principle, be arranged as a triangle, as shown in U.S. Pat. No. 4,993,040. Furthermore, U-shaped arrangements are also possible.
FIG. 9 of DE-OS 4,029,187 describes a power laser of polygonal configuration with mirror blocks in the corner regions, which mirror blocks have an essentially monolithic body, and intermediate blocks in the straight paths between the mirror blocks, which intermediate blocks have an essentially monolithic body. At least one straight partial bore is in each mirror block. A respective through bore is in each intermediate block. The mirror blocks and the intermediate blocks are fine-machined for the gas-tight and centered mounting of laser tubes. And an optical bench having corresponding corners carries the mirror blocks and the intermediate blocks on its periphery. The problem is common to all lasers of this kind that they will be switched on and off, even in succession, like a normal machine. The laser according to DE-OS 4,029,187 has very many outstanding properties. The mode of the laser beam is time stable and practically does not change during operation. However, the optical bench, constructed as a framework of special steels, has to be welded together. The framework struts are hollow and therefore costly to join together by welding. The whole optical bench is filled with water, which must be kept very constant in a large volume. Care must therefore be taken that the same temperature is present at all places of the optical bench, at least in the water. This requires the expense of flow technological means, because the water flows along the path of least resistance if no special precautions are taken. Joint surfaces are required between the optical bench and the blocks--whether they are mirror blocks or intermediate blocks--and have to be machined with high accuracy and also have to have a highly accurate spatial orientation. A joint surface on the optical bench and one on the block are respectively provided. These must then be secured by locating pins. Only on completion of this can it be seen whether everything is really fitted and seated properly.